I present fresh data that show the leading role played by smallholder peasants in land‐use intensification, technical improvement and landscape transformation in Maresme County (province of Barcelona, Spain) between 1850 and the 1950s. As a reaction to their precarious situation, caused by an unequal landownership distribution (which is assessed by looking at the minimum‐income and maximum workable farm sizes), smallholders drove agrarian changes in this coastal Mediterranean area. The results of their individual efforts, and their collective action through social mobilization and cooperatives, entailed a socio‐economic and political improvement, especially in denser populated areas closer to markets, until the arrival of Franco's regime.